SU1578456A1 - Device for multiple reflections in double-reflecting interferometer - Google Patents

Abstract

The invention relates to a measurement technique and can be used in interference devices for measuring movements and speeds of movements. The aim of the invention is to increase the vibration resistance and spatial resolution due to the concentration of radiation along the direction of propagation. The radiation of the source is divided by the beam splitter into two beams, and after multiple reflections from the mirror, the beam hits the beam splitter, where it is combined with the reference signal coming from the reflector and forms an interference pattern. When used as an optical collecting element, the reflector is placed on a straight line passing through the centers of the mirror and lenses at a distance from the center of the lens equal to R = F / (AF) [D 2 + Y 2] 1/2, where F is the focal length of the lens, A is the distance between the mirror and the lens, Y is the distance from the mirror to the optical axis of the lens. When a concave mirror is used in the device, the flat reflector is placed at distances x: R = F / (AF) √ Y 2 + A 2 is from the center of the concave mirror and Y 1 = -YF / (AF) from its optical axis. The specific form of the reflector is determined by the need to ensure coincidence of the ray paths of the informative and reference beams when they are added together. 1 hp f-ly, 2 ill.

Description

The invention relates to a measuring technique and can be used D interference devices for measuring displacements and speeds of displacements, mainly for registering rapidly occurring processes — ultrasonic vibrations, acoustic emission signals, shock waves.

The purpose of the invention is to increase vibration resistance and spatial resolution by concentrating the radiation along the propagation direction.

FIG. 1 is a diagram of a Michelson interferometer with a device for multiple reflections containing a collecting lens; in fig. 2 - a mirror in the opposite direction.

The interferometer contains a source of monochromatic radiation, for example, a helium laser, a beam splitter 2 5 device 3 multiple reflections containing a collecting element 4 in the form of a lens (Fig. 1) or a concave mirror (Fig. 2), a flat reflector 5 and mirror b, St. with a controlled object 7. The reflector 5, when used as an optical collecting element of a lens (Fig. 1), is placed on a straight line passing through the centers of the mirror 6 and lens 4 at a distance from the center of the lens equal to

f g l g-

g g a + u j

and f, u -1

/ 2.

where f is the focal length of the lens; a is the distance between the mirror and

LENS;

j is the distance from the mirror to

the lens axis. When using a concave mirror (Fig. 2) in the device, the flat reflector 5 is placed at a distance x25

-,. „Ј

-: f-N

corner i-ag

from the center of the concave mirror and

j f

Have

a - f

 ; go optical axis.

The interferometer also contains a reflector 8 in the form of an angular reflection unit (Fig. 1) or in the form of a flat grcal (Fig. 2) and a block 9 for receiving and containing the interference signal. The specific type of reflector 8 is determined by the need to ensure coincidence of the ray paths of the informative and reference beams when they are added. Additional flat mirrors 10 and 11 can be used to match the optical schemes of the device and the interferometer (Fig. 1).

The radiation from source 1 is divided by a beam splitter into two beams, one of which is directed to the reflector 6, and the other into the device 3 multiple reflections on the mirror 6. After reflection from the mirror, this beam is deflected by the collecting optical element 4, falls on the reflector 5 and returning after the secondary deflection the collecting element 4 to mirror 6. After multiple reflections from the mirror 6, the beam hits the splitter 2, where it is combined with

0

five

0

$ 0 5

Q

the reference signal coming from the reflector 8, and forms the interference pattern, which is recorded by block 9.

The invention makes it possible to increase the vibration resistance of the interferometer by reflecting the rays reflected by the mirror 6 to be collected by the optical element 4 on the mirror, thanks to which the probability of interfering rays leaving the sensitive area of the photodetector is reduced. At the same time, the spatial resolution of the device is increased, since the reflection of all rays comes from a small portion of the surface of the mirror 6.

By turning the reflector and turning it together with the collecting element 4 relative to the centers of mirrors 5 and 6, it is possible to vary the number of reflections from mirror 6, and thereby change the sensitivity of the interferometer.

Claims (3)

1. A device for multiple reflections in a double-beam interferometer under control, comprising a mirror for mounting on an object, an optical collecting element and a reflector, characterized in that, in order to increase the vibration resistance and spatial resolution, the reflector and the mirror are located at the conjugate points of the collecting element and the reflector is flat and installed with the possibility of rotation relative to its center and joint rotation with the collecting element relative to the center of the mirror. 2. The device according to claim. Characterized in that the collecting element is designed as a lens, the reflector is placed from the center 1 of the lens at a distance r equal to g a - f . "four where f is the focal length of the lens; a is the distance between the mirror and a lens; y is the distance from the mirror to the optical axis of the lens, and the mirror, the lens, and the reflector are located so that their centers lie on the same straight line. 3. The device according to claim. 3, wherein the collecting element is designed as a concave mirror, and the reflector is placed from the center of the concave mirror at a distance g equal to a - f L + a and from Scientific research institute its optical axis at a distance of 1 y f a ™ where f is the focal distance of the concave mirror; a is the distance between the reflector and a concave mirror along the optic edge; y is the reflector distance to op. the tic axis of the vaggut mirror. FIG. 2